A preliminary clinical trial suggests that gamma vinyl-GABA (GVG) -- a drug used to treat epilepsy -- may offer a potentially effective treatment for cocaine addiction. The study was funded by the National Institute on Drug Abuse, the National Institutes of Health.

A small, preliminary clinical trial conducted in Mexico showed this drug could cut cocaine use dramatically in people who had used cocaine daily for at least three years.

The data reported in this study support the need for a larger, double-blind, placebo-controlled trial to determine the true efficacy and safety of this drug for cocaine addiction, the authors say.

"GVG reduces levels of dopamine, the 'feel-good' chemical that floods the brains of cocaine users, providing the 'high' they crave," says Dr. Frank Vocci, Director, Division of Treatment Research and Development, National Institute on Drug Abuse. "Using GVG to temper the dopamine system may very effectively block the addiction-related effects of cocaine."

A total of 19 men and 1 woman entered the study. Eight people completed the trial in which they received escalating doses of GVG for the first week until they reached the highest dose of 4 grams per day.

The eight people who completed the study said their craving for the drug was eliminated after 2-3 weeks of continuous GVG administration, the authors report. In addition, those who completed the trial also showed improved self-esteem, reestablished healthy family relationships, went to work, or actively sought work.

GVG, also known as vigabatrin, is approved in many countries as a treatment for epilepsy. Its main effect is that it increases the amount of another brain chemical involved in nerve cell communication, GABA, and thus helps moderate seizures. The U.S. Food and Drug Administration has not approved GVG for treating epilepsy or any indication because of concerns about the relatively high incidence of tunnel vision that has occurred in people given the drug over many months or years. Although none of the eight people who completed this study reported vision changes, the effects of vigabatrin on the eye have been of sufficient concern to relegate it to second-line status in countries where it is marketed, and to prompt the requirement of regular follow-up by an ophthalmologist.